Aircraft and other aerial vehicles are frequently monitored by radar equipment. Aerial vehicles having a low radar signature have been developed to evade this monitoring, i.e., aerial vehicles that, for example, radiate back radar waves only at a low level in the direction of the radar equipment.
A low radar signature, which is the equivalent of a low probability of the aerial vehicle's being detected by radar, can be implemented or at least enhanced, for example, by energy-absorbing paints, energy-diverting seals for the outer-skin joints, fewer and larger hinged flaps for maintenance instead of many small ones, accommodating loads within interior shafts instead of having exterior loads.
Ninety percent of the improvement, i.e., the reduction in the radar signature of an aerial vehicle, currently occurs by improving the geometry of the aerial vehicle. This can be effected, for example, by reducing edge reflections whereby the edges are, for example, parallelized.
Examples of stealth aerial vehicles having an extremely low radar signature include the strategic long-range bomber Northrop B-2, and the unmanned aircraft Boeing X-45 and Northrop X-47.
In aerial vehicles having an extremely low radar signature, any disturbances in the aircraft surface can generate unwanted radar back-scattering. These disturbances can include, specifically, engine intakes and nozzles, as well as landing gear and weapons bay doors, the stealth concealment of which can entail a significant cost even when in the closed state.